Flails

Flails are tools and/or weapons that can be used as agricultural tools or weapons in a fight.

Types of flails

The most common flail is the Grainflail. It can be crafted with "shift+M" key command and "Utily articles" selection from the menu.

The Small Flail is a smaller, lighter version, also usable as a close combat weapon.

The rarer Ball & Chain and Warflail are specialiased as proper, purpose-built weapons, rather than tools also usable as weapons.

URW Game Encyclopedia description

The official URW in-game encyclopedia (accessed by the F1 key) describes flails (in general) thusly:

Flails are threshing tools for separating the usable parts from the rest of the harvested plant, but flails can be also used as a weapon. Threshing itself is one of the actions covered by agriculture skill.